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Node js


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  • 1. Node js with npm, installing express js @RohanChandane Last updated on 13th Oct 2013
  • 2. Installing Node
  • 3. Hello World
  • 4. ... On windows machine, - Setting up environment variable is built in inside nodejs directory - after installation, type nodevars to install environment variable. nodevars.bat is a batch file responsible for setting it up
  • 5. What is Node / Node js? - Node is Command line tool - Download it and install - It runs javascript code by typing ‘node your-script-file.js’ - Hosted on V8 Javascript engine - uses V8 as standalone engine to execute javascript. - Server-side javascript - Node provides JavaScript API to access network & file system. - These JavaScript files runs on the server rather than on the client side - We can also write a server, which can be a replacement for something like the Apache web server
  • 6. ... - Uses event-driven I/O (non-blocking I/O) - is just a term that describes the normal asynchronous callback mechanisms. - In node.js you supply callback functions for all sorts of things, and your function is called when the relevant event occurs. - So that means, it works parallelly on different I/O operations. - eg. Code for reading from a file & reading values from a database can be executed one after another (since node js is single threaded), and it will wait for data to receive from file & database. Once it receives data, it will call callback function related to function call. - One language - to write server side and client side code - No need to learn server side language like Java & PHP
  • 7. Why Node 1. Efficiency - Response time = server-side script execution time + time taken for I/O operation - Node reduces the response time to the duration it takes to execute the slowest I/O query - Its mainly because ‘Single threaded - Event loop’ - Also called Event driven computing Architecture - There is a need for high performance web servers
  • 8. ... 2. JavaScript - JavaScript is universal language for web developers - Its single threaded - Its dynamic 3. Speed - Up till now, JavaScript was related to browser - We used it for DOM manipulation - and our favourite browser to execute javascript, is Chrome
  • 9. ... - Chrome uses V8 engine underneath to execute js - V8 is the fastest javascript execution engine - V8 was designed to run in Chrome’s multi-process model V8 engine - V8 is intended to be used both in a browser and as a standalone high-performance engine
  • 10. Asynchronous callback mechanisms 4. callbacks are invoked functions, which are initiating - I/O operations - writing to a socket - making a database query & not going to return the value immediately event loop 3. event occurs 1. registers callbacks 2. loop wait for events There's a single thread, and a single event loop, that handles all IO in node.js
  • 11. Writing Server-side js with Node Now, lets see how to write a server in JavaScript - creating 'server.js' var http = require("http"); http.createServer(function(request, response) { response.writeHead(200, {"Content-Type": "text/plain"}); response.write("Hello World"); response.end(); }).listen(8888); - executing it: node server.js
  • 12. Passing function as parameter lets say function execute(someFunction, value) { someFunction(value); } execute(function(word){ console.log(word) }, "Hello"); can also be written function say(word) { console.log(word); } function execute(someFunction, value) { someFunction(value); } execute(say, "Hello");
  • 13. Understanding server.js var http = require("http"); function onRequest(request, response) { console.log("Callback invoked"); response.writeHead(200, {"Content-Type": "text/plain"}); response.write("Hello World"); response.end(); } 1 2 http.createServer(onRequest).listen(8888); console.log("Server started"); 3 4 single thread
  • 14. ... This ‘server.js’ program executes in following order 1. registers callbacks onRequest 2. loop wait for events listen(8888) 3. event occurs Browser requests - localhost:8888 4. callbacks are invoked function onRequest() gets execute
  • 15. Some Basic Core Modules Node has several modules compiled into the binary. Defined in node's source in the lib/ folder. To load use require('modules identifier') - HTTP how to use require('http') - Net how to use require('net') - DNS how to use require('dns') - Events how to use require('events') - Utilities how to use require('util') - File System how to use require('fs') - Operating System how to use require('os') - Debugger how to use debugger
  • 16. Some Global object Available in all modules - Console how to use console - Process how to use process - Exports how to use exports - require how to use require() - setTimeout how to use setTimeout() - clearTimeout how to use clearTimeout() - setInterval how to use setInterval() - clearInterval how to use clearInterval()
  • 17. Core Modules: usage Net require('net') - Asynchronous network wrapper. It can create server & Client. - Following example program creates server. It can be connected using Telnet/Putty & responds to all user provided data. var sys = require("sys"), net = require("net"); var server = net.createServer(function(stream) { stream.setEncoding("utf8"); stream.addListener("connect", function() { stream.write("Client connectedn"); }); stream.addListener("data", function(data) { stream.write("Received from client: " + data); stream.write(data); }); }); server.listen(8000, "localhost");
  • 18. Node Package Manager
  • 19. NPM: Node Package Manager (NPM) - Node modules largely written in JavaScript which runs on the server (executed by the V8 engine) rather than on the client side. - These modules are registered in npm registry at - To use these modules while developing application, npm helps in - installing Node js packages / Modules / Programs - & linking their dependencies - npm is a command line utility program - npm is bundled and installed automatically with Node version 0.6.3 and above - On windows, after setting up environment variables npm command can be executed from any desired location to install node packages
  • 20. NPM Commands npm -l - display full usage info npm <command> -h - display quick help on command - eg npm install -h npm faq - commonly asked questions npm ls - displays all versions of available packages installed on system, their dependencies, in tree structure
  • 21. … npm install <module name> - to install new modules - on windows, command prompt should be running with admin rights npm install <module name> -g - to install new modules globally - on windows at location C:Users<user>AppDataRoamingnpm
  • 22. ... npm update - update all listed packages to their latest version (in given folder) - install missing packages - removes old versions of packages npm update -g - update all listed global packages npm update <pkg> - update specific package
  • 23. express js
  • 24. Installing node module: express js - express js - Web application framework for node js - Provides robust set of features to build single and multi page, & hybrid web application - installing express js on windows - Start cmd with admin rights - Make sure you have set up environment variable for node js - Go to your project directory and type npm install express
  • 25. ... - installing express as global package - Previously we installed express for particular folder - But usually we install it globally - To install express globally, type npm install express -g - On windows, this will install express in C:Users<user>AppDataRoamingnpm - express js is ready to use now
  • 26. ... - Create a express project - Inside project directory type express and enter - This will create a project structure and will display created files, what are dependencies and how to run project - This is instructing to install dependencies by staying in same directory and type npm install
  • 27. ... - Run express server - To run this newly created project, type node app - Go to browser and type localhost:3000 And now you can start editing code to make it the way you want.
  • 28. ... - While setting up project - you can pass certain parameters to choose templating engine and stylesheet engine - for example, following command will create project with support for ‘less’ stylesheet and ‘ejs’ templating express -c less -e Off course it need to install dependencies
  • 29. References Book: Node: Up & Running - Tom Hughes-Croucher & Mike Wilson (O’reilly)